i've placed a kernel that works on my U5 at:
ftp.netbsd.org:/pub/NetBSD/arch/sparc64/kernels/NetBSD-1.5R
this hopefully should work for you.
.mrg.
ps: there is another issue i've noticed looking at this problem. the
onboard `hme' probes as `hme1' on the e250 because of the hard coded
hme0 for the U5/U10 onboard. perhaps the right solution would be to
force the two simba busses on the U5/U10 (US-IIi) port to be numbered
the other way? then everyone would have the onboard hme on pci1.